A known method of personal identification is the fingerprint. Due to the extreme diversity of the individual features contained in a fingerprint, it stores such a large "personal data record" that it can be considered an unmistakable, forge-proof means of identification. An advantage is that it cannot be lost and that it is always available. The identification systems based on fingerprinting are often extremely complex, however.
DE-PS 3712089 describes a solution for such complexity whereby a finger positioned on a finger support is scanned by means of sensors and a light-pulse source; the sensor signals are analyzed in a computer circuit. The computer utilizes reading, comparison and storage of the identification information by an additional control computer. Although this solution is intended to provide the most compact configuration possible, identification systems based on this solution are still extremely complex and unsuitable for universal application.
A further known method of identification is that of electronically operating identification in the form of magnetic cards or chip cards used as check cards. An electronic key card, which opens several differently coded locks, is described in DE-OS 3628525: The key card contains a code at both ends and thereby enables access to be gained to at least two locks. The disadvantage of these cards is that they must be kept somewhere, and they can be lost, forgotten, stolen, etc.. Moreover, they are not immediately available and usable in every situation in life, including dangerous situations. A further disadvantage is that they require space-and cost-intensive analysis stations and that they are sensitive to mechanical deformation and damage.
Swiss patent specification 546 446 concerns a device employing data carriers to identify individuals by means of a testing station, the objective of which is to protect the identification data against duplication and unauthorized access. For this purpose, a mutual exchange of information sequences takes place between data carrier and testing station. The data carrier and testing station compare the information sequences with their respective stored information sequences, whereby the testing station generates a "good-signal" when the sequences match. This Swiss patent provides a solution for data communication between data carrier and testing station, but complex information generators with memories, comparators and switches are required on both sides. A disadvantage here is the extensive scope of electronic circuitry equipment required and the consequent high production costs and restricted range of application. Universal application for a large number of different applications, some of which may not arise until the data carrier is in use, is not possible here, as each case of application, i.e. each testing station requires its own protected memory areas in the data carrier, some of which would have to be programmed after the data carrier had been put into use. A similar solution is described in DE-PS 2224937.
U.S. Pat. No. 3,971,916 describes a means of identification in the form of a portable memory unit designed primarily for bank applications, in which a personal, secret identity number, the number of the bank account and further personal data are programmed when the unit is issued to the holder, whereby the unit can be designed as a ring to be worn on the finger. Disadvantages are the programming required for each case of application and the limited data capacity of the memory unit, which represents an obstacle to universal use.
DE OS 2657182 describes a means of identification in the form of a data carrier which transmits information stored in the data carrier to an analysis unit as a result of energy coupling with the analysis unit. The data carrier can he designed as a ring to be worn on the finger, which is supplied with energy from the analysis unit. A disadvantage of this solution is the limited amount of information in the data carrier, which cannot remain secret and which requires allocation and monitoring for several users. Accordingly, this patent's teaching is not suitable for universal application.
A common feature of these known solutions is that the identity and the codes authorized to investigate the identity must in each case be programmed into the means of identification. Such programming, in addition, must be done in a manner specifically relating to the individual application. Comparison is required in the programming and, as a result modifications and monitoring requirements make the solutions unsuitable for universal use, nor are they independent of any specific applications. Furthermore, none of the known means of identification enable the identity-related data to be protected, i.e. data coding.
Data coding systems are known whereby the communication partners possess the same key information, e.g. in the form of random information, on data carriers; and such partners use this key information to encode/decode messages directly, bit by bit, whereby the bits of the key information are used once only. A disadvantage of these systems is the very high level of requirement for key information, together with synchronization problems between the communication partners.
Coding systems are also known which solve the problem of the bothersome requirement for key information by means of key generators, which generate key information to be mixed with the plain text on the basis of various basic keys. A disadvantage of these systems is the problem of keeping these basic keys, which are to be replaced at intervals, secret.
European patent application 0 022 069 specifies a solution to this above-identified problem, (involving constant renewal of these keys at the place of encoding/decoding) by separate, isolated key containers with a key capacity of approx. one year. OS 3340582 describes a similar, improved key storage module, consisting of a key generator and a loadable and erasable source-key storage unit, whereby the key generator processes the internal source keys in the module, which cannot be read externally, with a supplementary key provided externally by the key unit and passes the result on to the key unit as a basic key. A disadvantage of these two solutions is the limited effective life of the keys, which necessitates re-loading of the key storage units in the course of time.
Devices known as pseudo-random generators for coding systems include the multi-stage feedback shift registers specified in PS 2451711 and OS 3732432, whereby the key is determined by the number of stages and the configuration of the feedback system, i.e. the hardware circuitry. These systems are not suitable for universal use for varying applications because the message transmitter and receiver require the same device. Furthermore, the feedback operations of the shift registers limit the operating speed of these systems.
PS 3129911 describes a pseudo-random generator in the form of a read/write memory loaded with random information, from which this random information, addressed via a loadable address counter, is read out. This solution is unsuitable for coding operations, as the random information of this generator is simple to establish.
The common disadvantage shared by all known coding systems is that their key sources do not remain permanently stable and that they are limited to a specific application.
DE 3009317 and DE 3311665 describe a hybrid associative storage system, consisting of a non-associative base memory divided into sub-memory units, whereby these sub-memory units are connected cyclically and in succession via a connection device to an association matrix functioning as an associative search surface, in order to reduce the search times.
DE 3539026 provides a solution for a fast-operating search process for such hybrid associative storage systems.
A common characteristic of these known associative storage systems are the time-consuming search processes required for memory access, whereby the aim of the known solutions is to increase the size of the search surface and to accelerate the search process by means of suitable circuitry and data-structuring. The search times and internal connections of these storage systems increase substantially as the storage capacity is extended, as a result of which these systems are often too small or complex for data-base applications, for example.
Additional prior art of interest include the following literature references:
(1) L. E. Stanfel "Practical aspects of doubly chained trees for retrieval" Journal of the Association for Computing Machinery; vol. 19, no. 3, July, 1972, pages 425-430. PA1 (2) Lewis/Smith "Datenstrukturen und ihre Anwendung" 1978 R. Oldenbourg Verlag publishers, Munich PA1 (3) J. Niedereichholz "Datenbanksysteme, Aufbau und Einsatz" 1981 Physics Verlag publishing company, Vienna
The document, "Practical aspects of doubly chained trees for retrieval" (1) describes doubly chained trees, the nodes of which each store two addresses and a key definition which is searched for in the tree. Searching is carried out serially, character-by-character, by comparing the search argument with the stored key definition, whereby the next nodal level is addressed for the next search argument character when the search argument and the key definition match (son-indicator address), and if they do not match the search is continued at the neighboring node on the same nodal level (brother-indicator address), until either the sought key definition is found or the required new key definition is finally stored at the end of the chain.
Similar search trees are known in the form of B-trees, binary trees, sorted binary trees, chained lists, etc. (See references 2, 3). They differ in the number of branches which emanate from a node and in the chaining principles. A common characteristic shared by all these, however, is the required search process by means of character-by-character comparison of a search argument with stored key definitions.